The monitoring of the cardiac activity is necessary in all serious pathological and cardiac cases and in all emergency cases inasmuch as the monitoring allows gathering of information on the momentary condition of the patient.
Additionally, the patients and sick susceptible to cardiac disturbances, and notably to disturbances in the cardiac rhythm, necessitate attentive monitoring depending on the seriousness of their condition.
Actually, arrhythmia generally leads to serious disturbances that may, in certain conditions, lead to the fibrillation of the myocardium, an extremely serious condition that only an electric defibrillation shock can modify.
A fibrillation corresponds to a total desynchronization of the excitation of the cardiac fibers, caused by excitation loops that close on themselves. A self-sustaining movement is created in these loops, called reentrant loops, preventing all new excitation of the cardiac muscle.
A local fibrillation in the auricles (auricular fibrillation) is not deadly and may be reduced by an electric shock.
Localized in the ventricles, this fibrillation (ventricular fibrillation) completely stops the functioning of the heart. Indeed, the mechanical contraction of the heart practically no longer occurs. This total hemodynamical ineffectiveness causes death in the three to five minutes following the onset of the disturbance because of a lack of cerebral irrigation. Only a defibrillation electric shock can resynchronize all of the cells of the heart.
This treatment consists in applying through the thorax, by two electrodes, a short duration current of a few tens of amperes at a few thousands of volts for a few milliseconds resulting from the discharge of a capacitor.
Since a few years ago, the defibrillators have been equipped with a cardiac monitor to visualize the signal of the electrocardiogram, abbreviated ECG, before and after the defibrillation shock.
Actually, ventricular fibrillation is responsible for most of the deaths occurring during the course of the pre-hospitalization phase of myocardial infarction, without rapid intervention and appropriate emergency equipment. Indeed, present arrhythmia detectors are complex, not transportable, and necessitate the presence of a physician to recognize the fibrillation pathology.